V50 2.4 poor idle and stalling only when hot

johna · 2020-07-27T08:04:08+00:00

What does it run like after you have warmed it up and let it sit for a while?

johna

Well, after waiting a month (or was it two?) for my DICE clone so I could check codes in VIDA it finally arrived and after some effort in getting it to work I don't really have any useful information.

There were a few errors as expected, and the only ECM codes were ignition coil and misfire. After clearing the codes none of them returned except CCM-0071 (climate control system).

I let the car run for some time with the idle problem present and near stalling but no new codes showed up.

I don't know what to do next. I'm leaning towards taking it to a Volvo dealer or specialist although I'm worried they will just throw parts at it until it is fixed (at my expense). Anybody have any ideas or can recommend someone convenient to Blue Mountains/Western Sydney?

timbo

Now you have vida you can have a clearer picture of what's going on with the car.

I usually start by checking the "freeze frame details" of each fault code, for anything wildly out of spec. ( If unsure of what normal readings for each sensor should be, they are listed in the VEHICLE COMMUNICATION > ECM > parameters > description tab)

You can do this only in the "initial state" tab of the fault trace window.

Click on a fault code to highlight it and the click "details" down the bottom.

Each fault code also logs various parameters to try and help with diagnosis.

Also you can click "details" and it will give you more information about the fault code including possible source

Further to that you can look up the specific fault codes in the information > fault tracing tab, there will often be step by step instructions and diagnostic tests for each fault code.

The red communication code for the BCM is concerning...

johna

None of the fault codes except for one of the climate control ones has reappeared since erasing them, even though I drove the car with the problem happening.

The ECM coil and misfire codes only appeared on the delivery tab, they were not on the initial state tab so I could not get any further details.

Thanks for the screenshots - I will look into those.

Is it normal for these to run at 105 deg C or more without the fan on? The fan does work when i manually activate it using VIDA - what temperature should it come on, do you know?

timbo

I'm pretty sure they run a 92 degree thermostat so sounds relatively normal, Volvo runs the engines hot for fuel efficiency

When you run a scan it will automatically jump to delivery tab with the results, you can then click on initial state and see the faults, but if you scan it again after clearing faults it erases the previous readout.

Taking photos of the faults for reference, as you have done, is a good idea.

Have you tested engine compression at all?

johna

Have I tested engine compression? No. That scares me that you asked? Would it run and drive fine and just have an idle issue when hot if it had a compression problem?

I bought the car with these problems so anything is possible. It was very low on oil when I picked it up and coolant was also low so was not very well cared for.

johna

Update to this thread: after my last testing with VIDA I found a radiator hose had split and lost a bit of coolant so had to order a new hose and have just fitted it today. At the same time I fitted new spark plugs because I finally got around to checking them and they looked pretty tired.

So I ran the car again today and it ran better - still idled badly when hot, but less likely to stall. A friend working on it with me said that might be a sign of a bad coil - that it improved a bit with new plugs. I did run it again an hour or two later and it was stalling more like usual though so as usual not very conclusive.

I still find it real strange that it won't idle properly and will stall at idle, but if I roll down a hill in neutral it will sit there at ~800rpm same as when idling and run perfectly. Wonder what is different about a stationery idle and a moving idle?

I plugged it back into VIDA and I now have ECM-3502 Misfire emission related multiple cylinders. It's on the delivery tab and the initial state tab. Based on what's in VIDA and as posted by @timbo above, there is quite a few things to check :(

c30c30

Rolling down a hill is ok? What about idling while stationary on an incline? PFS?

johna

c30c30
Rolling down a hill is ok? What about idling while stationary on an incline? PFS?

I should have mentioned that. Idling when stationary on a hill up or down is bad. It seems to be good only if moving (probably ok rolling up hill too but hard to roll too far up hill) - I suspect there is a different idle mode for moving and another for stationary. My previous (manual) BMW used to idle slightly higher until it came to a full stop and then it would lower slightly. I think it is an emissions thing.

PS. Volvo is manual too.

carnut222

Could it be something odd about the vehicle speed sensor? I mean all I really know is on the earlier 240s with LH2.4, if they didn't get a vehicle speed signal to the ECU, the idle would fluctuate. Your car seems odd though unless somehow the computer is not getting the signal to go into idle mode when the car is stopped? Strange...

johna

You could be on to something. Every now and then I get an ABS warning light when the problem is happening. That could be wheel speed-sensor related. I haven't actually found any stored ABS error codes to tell me why though strangely (maybe I am not looking in the right place though).

I will investigate that further when I next plug in VIDA and look for codes or watch the live data of the speed sensors.

I've also just found the live data for misfires and found that the car is registering misfires when the problem is happening. I don't know if that is cause or effect though. As you can see in the linked video below the misfires are mostly cylinders 2, 3 an 4. So I am going to swap a couple of the worst ones around (3 to 1, 4 to 5) and see if the misfire moves.

I think there's a few clues here with misfires and ABS - I've just got to figure out the puzzle.

https://www.youtube.com/watch?v=pQj6a3egeHY

(that's it idling on its own first, then me revving it a little and trying to hold it around 900pm, then letting it try and idle itself again)

c30c30

If it's anything like the C30's then random ABS issues can be battery / voltage issue. How's the alternator / battery and earthing? Your screenshot shows only 13V at 1,200rpm which seems a little low.

johna

Voltage typically shows at mid-to high 14 V when driving and when idling normally. When the problem is happening it does fluctuate but I don't know if that is cause or effect either - I assume that if the car is struggling to run and cycling up and down between 0 and 800 rpm then the voltage would cycle similarly???

Not sure about that 13V value in the screenshot - that appears to be what it recorded when the problem first happened. Yet another thing I need to check and watch closely.

I've checked as many earths as I can find and all look good and tight.

I just tried the coil swap and the misfires did not move - still on same cylinders.

I also checked vehicle speed live data and individual wheel speeds and all reported what looked like normal consistent values - vehicle speed 0km/h, wheels speeds all 0.67km/h.

I still cant find any stored ABS faults, even though the light was on.

Thanks for all of the advice.

johna

The most frustrating part of this problem is that when I research all the possible problems there is one thing that does not make sense: why will the car will fail at idle but it will run fine at a similar speed to idle if I lightly hold the throttle pedal or when the car is rolling in neutral?

Possibilities like faulty coils, low compression, intake leaks, blocked PCV, various sensors, leaking valves... they just don't make sense to me.

c30c30

It's an odd one.

When you're rolling down hill do you have your foot on the brake? In years gone by, I seem to recall idle / stalling issue caused by brake booster.

johna

I've rolled both with brakes on and off and it idles fine either way.

I also struggle to think this is vacuum leak problem (although I've checked) because when I got this car the cylinder cover to PCV hose was completely broken and it ran fine, and on one test drive I forgot to reconnect the vacuum hose on the right side of the engine and it drove normally. Weird.

johna

Exciting news for anybody who cares (mostly me).

While diagnosing by cooling components with a garden hose I found that I could repeatedly stop the problem by cooling the crank sensor. I need to replace the part now but I'm pretty confident the problem may be resolved.

I'll report back when I know for sure.

johna

See that little device in the picture? That is a faulty crankshaft sensor (or RPM sensor in Volvospeak).

It took me two months to find that this was the cause of my idle/stalling issue but today I fitted a second hand sensor bought for $25 from Pick 'n Payless and the car is now running well.

No idea why the ECU couldn't throw a fault code for this like I expected it would. If the cam sensor and crank sensors don't agree it should be pretty obvious, shouldn't it?

All I need to do now is replace the timing belt, engine mounts, CV boots, fix the air conditioning, replace the leaking steering rack, get a wheel alignment, and whatever else breaks next... :)

Thanks for all the input and advice!

johna

I celebrated too soon. The problem went away for a few trips but returned. I am going to try a new connector.

johna

I celebrated too soon. The problem went away for a few trips but returned. I then tried a new connector.

Then I tried other things like disconnecting the electrical connection to the oil filter housing and I bought a throttle body. No good still.

Today I went with a new theory and put a thin washer under the crank sensor to raise it slightly and went for a good test drive and so far so good. I am not celebrating yet - will see how it is after a few longer drives.

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